php - 如何制作不同的 WHERE 子句

Question

$data['do'] = $this->db->query("SELECT MONTH(`date`) as month, COUNT(*) as count
FROM `simple` WHERE `ochistka` = 'somevalue' GROUP BY MONTH(`date`)");

在这里，我正在选择每个月都有一些值的字段，但是我如何才能选择一个具有其他条件的字段，而不是像 count( ) 作为计数，而是另一个 count( ) 作为 count2，具有其他 WHERE 子句是可能的？

Answer 1

如果我正确理解您要实现的目标，您可以使用 SUM(IF) 技巧，如下所示：

SELECT MONTH(`date`) as month,
       SUM(IF(`ochistka` = 'somevalue', 1, 0)) as count1,
       SUM(IF(`ochistka` = 'othervalue', 1, 0)) as count2
FROM `simple`
GROUP BY MONTH(`date`)

Answer 2

目前无法测试代码，但基本思路是使用子查询：

SELECT t1.month as month, t1.count as count1, t2.count as count2 
FROM
    (SELECT MONTH(`date`) as month, COUNT(*) as count
     FROM `simple` 
     WHERE `ochistka` = 'somevalue' 
     GROUP BY MONTH(`date`)) AS t1
INNER JOIN
    (SELECT MONTH(`date`) as month, COUNT(*) as count 
     FROM `simple` 
     WHERE `ochistka` = 'someothervalue' 
     GROUP BY MONTH(`date`)) AS t2 ON t1.month = t2.month